Vertigo has been of special interest in our research. While it can be induced by various etiological factors, a basic dualism in its pathogenesis is evident.

Many patients with vertigo have been found to experience wide variations in the intensity of the symptom. Some have exacerbations in the morning, others in the evening. This observation suggested a possible dual pattern and we investigated vertigo by the same method used for the study of pathological pain.

In patients with vertigo, the intensity was determined at hourly intervals by using either a scale ranging from 0 to 10, or a series of qualifications, such as none, slight, moderate, severe, very severe and unbearable. At the same intervals, urine samples were collected and their pH values measured. Data were plotted in curves having time as common abscissa. Here again, as for pain, two different correlations could be observed. In some cases, the two curves—one for intensity of vertigo, and the other for urinary pH level—showed parallel variations. (Fig. 25) The vertigo became more intense when the pH was high, and this was considered to be vertigo.

Shows the curves of the intensity of vertigo

Fig. 25. Shows the curves of the intensity of vertigo and of the urinary pH in a case with an alkaline pattern, the variations of the two curves being parallel. (B. Welt, AMA Archives of Otolaryngology, 55:273-300, 1953.).

Vertigo with an acid pattern

Fig. 26. Vertigo with an acid pattern. The symptom is more intensive when the urinary pH values are lower. (B. Welt AMA Archives of Otolaryngology, 55:273-300, 1953.) of an alkaline pattern. In other cases—of an acid pattern—vertigo was more intense with lower values of urinary pH. (Fig. 26).

The acid base pathogenesis of vertigo was further confirmed by the response to acidifying and alkalizing agents. B. Welt has widely investigated vertigo by this method. He also has used the response to therapeutic agents as a criterion for the pattern present. The administration of butanol, heptanol or unsaturated fatty alcohols was seen to induce an increase in the intensity of vertigo of acid pattern and a decrease in the alkaline type. Agents such as sodium thiosulfate have an opposite effect.

The analysis of the concomitant changes in the curve of the intensity

Fig. 27. The analysis of the concomitant changes in the curve of the intensity of the auditive acuity and of the urinary pH shows opposite variations in a subject with impaired hearing. The opposite variations are especially manifest for some values 2000 cycles in this case. This relationship corresponds to an acid pattern. (Courtesy of Dr. B. Welt.).

The great similarity in the response of pain and vertigo to the same agents has established the role of acid base changes in the pathogenesis of vertigo as well as the possibility of influencing these changes in order to relieve the symptom. These studies have shown that, in spite of the variety of etiological factors which can induce vertigo, the condition can be considered, from the point of view of therapy, in terms of its dualistic pathogenesis. This has simplified the therapeutic approach, limiting it to a choice between only two groups of agents. We will see later how successful this approach has been in Welt's hands.

The administration of an acidifying agent—2 grams of monoammonium phosphate—induces

Fig. 28. The administration of an acidifying agent—2 grams of monoammonium phosphate—induces a marked increase of the hearing acuity if the abnormality present corresponds to an alkaline pattern. Only minimal or no changes are seen to occur if a few drops of acetic acid are used as placebo. (Courtesy of Dr. B. Welt.).

Fig. 29. Alkaline pattern of hearing impairment corresponds to an increased hearing acuity following the administration of 2 grams of ammonium phosphate.

Alkaline pattern of hearing impairmentAlkaline pattern of hearing impairment

Fig. 30. Alkaline pattern of hearing impairment.